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    <title>glBeginTransformFeedback - OpenGL 4 Reference Pages</title>
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    <div class="refentry" id="glBeginTransformFeedback">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glBeginTransformFeedback — start transform feedback operation</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glBeginTransformFeedback</strong>(</code>
              </td>
              <td>GLenum <var class="pdparam">primitiveMode</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glEndTransformFeedback</strong>(</code>
              </td>
              <td><var class="pdparam">void</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters for <code class="function">glBeginTransformFeedback</code></h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>primitiveMode</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the output type of the primitives that will be recorded into the
                    buffer objects that are bound for transform feedback.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader).
            Transform feedback is said to be active after a call to <code class="function">glBeginTransformFeedback</code>
            until a subsequent call to  <code class="function">glEndTransformFeedback</code>.
            Transform feedback commands must be paired.
        </p>
        <p>
            If no geometry shader is present, while transform feedback is active the <em class="parameter"><code>mode</code></em> parameter to
            <a class="citerefentry" href="glDrawArrays.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a> must match those specified
            in the following table:
        </p>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: left; "/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                            <span class="bold"><strong> 
                                Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
                            </strong></span>
                        </th>
                <th style="text-align: left; border-bottom: 2px solid ; ">
                            <span class="bold"><strong> 
                                Allowed Render Primitive <em class="parameter"><code>modes</code></em>
                            </strong></span>
                        </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "> <code class="constant">GL_POINTS</code> </td>
                <td style="text-align: left; border-bottom: 2px solid ; "> <code class="constant">GL_POINTS</code> </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "> <code class="constant">GL_LINES</code> </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                            <code class="constant">GL_LINES</code>,
                            <code class="constant">GL_LINE_LOOP</code>,
                            <code class="constant">GL_LINE_STRIP</code>,
                            <code class="constant">GL_LINES_ADJACENCY</code>,
                            <code class="constant">GL_LINE_STRIP_ADJACENCY</code>
                        </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">
                            <code class="constant">GL_TRIANGLES</code>
                        </td>
                <td style="text-align: left; ">
                            <code class="constant">GL_TRIANGLES</code>, 
                            <code class="constant">GL_TRIANGLE_STRIP</code>, 
                            <code class="constant">GL_TRIANGLE_FAN</code>,
                            <code class="constant">GL_TRIANGLES_ADJACENCY</code>, 
                            <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code>
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
            If a geometry shader is present, the output primitive type from the geometry shader must match those
            provided in the following table:
        </p>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: left; "/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                            <span class="bold"><strong>
                                Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
                            </strong></span>
                        </th>
                <th style="text-align: left; border-bottom: 2px solid ; ">
                            <span class="bold"><strong>
                                Allowed Geometry Shader Output Primitive Type
                            </strong></span>
                        </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "> <code class="constant">GL_POINTS</code> </td>
                <td style="text-align: left; border-bottom: 2px solid ; "> <code class="constant">points</code> </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "> <code class="constant">GL_LINES</code> </td>
                <td style="text-align: left; border-bottom: 2px solid ; "> <code class="constant">line_strip</code> </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; "> <code class="constant">GL_TRIANGLES</code> </td>
                <td style="text-align: left; "> <code class="constant">triangle_strip</code> </td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="notes">
        <h2>Notes</h2>
        <p>
            Geometry shaders, and the <code class="constant">GL_TRIANGLES_ADJACENCY</code>, <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code>,
            <code class="constant">GL_LINES_ADJACENCY</code> and <code class="constant">GL_LINE_STRIP_ADJACENCY</code> primtive modes are available
            only if the GL version is 3.2 or greater.
        </p>
      </div>
      <div class="refsect1" id="errors">
        <h2>Errors</h2>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginTransformFeedback</code> is executed
            while transform feedback is active.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glEndTransformFeedback</code> is executed
            while transform feedback is not active.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated by <a class="citerefentry" href="glDrawArrays.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
            if no geometry shader is present, transform feedback is active and <em class="parameter"><code>mode</code></em> is not one of the allowed modes.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated by <a class="citerefentry" href="glDrawArrays.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
            if a geometry shader is present, transform feedback is active and the output primitive type of the geometry shader does not
            match the transform feedback <em class="parameter"><code>primitiveMode</code></em>.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glBeginTransformFeedback</code> if any binding
            point used in transform feedback mode does not have a buffer object bound.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glBeginTransformFeedback</code> if no binding
            points would be used, either because no program object is active of because the active program object has specified
            no varying variables to record.
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
                <span class="bold"><strong>OpenGL Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function / Feature Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.2</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.3</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.2</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.3</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.4</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.5</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                  <code class="function">glBeginTransformFeedback</code>
                </td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
                <td style="text-align: center; border-bottom: 2px solid ; ">✔</td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">
                  <code class="function">glEndTransformFeedback</code>
                </td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
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